This invention relates to a process for laser drilling holes in a cylindrical workpiece, more particularly laser drilling a row of holes while rotating the workpiece.
The laser drilling of holes, particularly when there are many holes to be drilled, can be a time consuming process. Each hole drilled is a discrete operation with adjustment to equipment needed before the next hole is drilled. For example, aircraft engine combustor parts, made from high temperature Ni or Co based alloys, can require tens of thousands of 0.020 inch (0.0508 cm) holes drilled at 20 degrees to the surface, where wall thickness may vary from 0.020 inch (0.0508 cm) to 0.100 inch (0.254 cm). In order to timely complete the entire process operation, monitoring and controlling the formation of each hole needs to be performed quickly. Even when the control and monitoring systems operate in substantially "real-time" as set forth in U.S. Pat. No. 5,026,979 this process is still time consuming.
Further when laser drilling holes into cylindrical workpieces, particularly turbine components such as combustors, these parts are not manufactured perfectly round and when drilling holes at steep angles, eg. 20 degrees as is typically required for these components, any variation in distance of the laser nozzle from the component surface can not only affect the laser focus and hole size, but position the hole incorrectly in the component.
Thus it becomes an object of this invention to provide a process for laser drilling holes in a cylindrical workpiece in a fast and accurate manner.